Extensive surface heat exchanger



Aug. 30, 1966 o ow c 3,269,459

EXTENSIVE SURFACE HEAT EXCHANGER Filed March 12, 1963 '7 Sheets-Sheet 1 g qluggp lm uuulllllllllm lllllllfllllllllllllllll lllllmlllliiiillllllll II I 37 37 FIGS FIG.6

\llllllllllllllll lllulIllllllllllllll"'lnlllll!" INVENTOR DRAGOLYOU B POPOVI TCH g/m, zZMfm, Jihad/4m! ATTORNEYS Aug. 30, 1966 13. PoPovlTcH EXTENSIVE SURFACE HEAT EXCHANGER '7 Sheets-Sheet 5 Filed March 12, 1963 I I III. Ill

\\ INVENTOR DRAGO LYOUB POPOVITCH Aug; 30, 1966 D. POPOVITCH EXTENSIVE SURFACE HEAT EXCHANGBR '7 Sheet s-Sheet 4.

Filed March 12, 1965 9 01 ONOE INVENTOR o o o v mm DRAGOLYOUB POPOVI TC H 4%:4, Mud/a1, Ml!

ATTORNEYS Aug" 30, 1966 D. POPOVRTCH 3,269,45

EXTENSIVE SURFACE HEAT EXCHANGER Filed March 12, 1965 7 Sheets-Sheet 5 FIGZZ FIG. 23 F1624 INVENTGR DRAGOLYOUB POPOV TC H ATTORNEYS Aug. 30, 1966 D. POPOVITCH EXTENSIVE SURFACE HEAT EXCHANGER Filed March 12, 1963 '7 Sheets-Sheet 5 FIG. 25

INVENTOR DRAGOLYOUB POPOVITCIH ATTORNEYS Aug. 30, 1966 D. POPOVITCH 3,269,459

EXTENSIVE SURFACE HEAT EXCHANGER Filed March 12, 1963 7 Sheets-Sheet 7 ATTORNEYS United States Patent 3,269,459 EXTENSIVE SURFACE HEAT EXCHANGER Dragolyoub Popovitch, North Tarrytown, N .Y. (37 Myers Ave., Denville, NJ. 07834) Filed Mar. 12, 1963, Ser. No. 264,516 18 Claims. (Cl. 165-140) The present invention relates to a novel and highly eflicient heat exchanger apparatus and components therefor susceptible to ready fabrication, and to a novel method of assembly appertainable to multi-component structures in general.

Each of the components assemblable into a heat eX- changer unit in accordance with the principles hereof is optimized in the characteristics essential to its intended purpose. The components are preferably arranged to be associated in modular units, which units collectively make up the heat exchanger apparatus. Efiiciencies heretofore unattainable are available in the present invention because of the optimum component design and the manner of associating such components to yield the useful heat exchanger apparatus.

Very briefly, a typical embodiment of the invention serves the purpose of transferring heat between otherwise isolated high and low pressure gaseous streams. The high pressure gas is confined to small diameter tubes alined in a plurality of spaced apart rows. Fins densely packed in spaced relation extend between the tubes of the rows to comprise the extended area. The low pressure gas is circulated along the fins in the spaces therebetween. The fins and tubes make up modular units adapted to be supported in frets which may include constraining shells and heavy insulation to isolate the assembly from the ambient environment.

Various assemblies of the aforementioned components along with headers, collectors and other tubes may be made to provide multi-channel heat exchangers, also capable of phase separations.

In general, heat exchangers find many industrial applications, at various temperature levels down to the cryogenic environments. However, in each application, the purpose of the exchangers is to effect heat transfer between two or more gaseous streams or flow under different pressures and in which each stream experiences a different pressure drop. These factors account, in part, for the different inlet and outlet temperatures of the gaseous streams, as determined under the operating conditions of the system in which they are incorporated.

It is therefore a fact that factors under such conditions, which must be considered in the satisfactory design or a heat exchanger of the type herein contemplated are the various heat transfer coefficients for each stream. Obviously, each stream must be provided with a different area of heat transfer surface to effect an efficient and economical heat transfer.

Refrigeration systems designed for ever decreasing temperatures emphasize the economy of materials and manufacturing costs because the work required to extract a given amount of heat from a body at a given temperature and to discharge it at a higher temperature increases in inverse relation to the temperature of the body. Thus, also, precautions must be taken to reduce heat leak to, or from, the external environment. Consequently, the heat exchanger apparatus must be designed for a very low 3,269,459 Patented August 30, 1966 temperature difference at its warmer end in order to reduce to a minimum, loss of extra costly refrigeration.

However, as is well known, for a given amount of refrigeration the required work is more than doubled if a gas, taken at ambient temperature, is expanded from a pressure of, for example, 1,000 p.s.i. rather than from a pressure of, for example, 3,000 p.s.i. It, therefore, becomes essential that the efficient heat exchanger must be capable of handling a high pressure gas on one side or pathway and a low pressure gas on the other side or pathway, with correspondingly adequate areas for the heat transfer surface therebetween.

The invention will further be described in connection with a consideration of well-known thermodynamic principles, as expressed in certain formulae, through which it is possible to detail the optimization of the various components and resultant assembly to realize efficiency of purpose. In the foll-owing coefficient to surface transfer area formula, it is known to write:

UVIZFI hO In this formula fouling effects have been neglected in arriving at a calculation for the value of U, for it is assumed that clean gases are employed in the heat exchanger. Also, of minor consequence, is the heat transfer resistance of the metal separating the streams, because, preferably, metals having very high thermal conductivity, relative to that of gaseous films, are employed.

In Formula 1, the usual definitions obtain, namely:

U=Overall heat transfer coefficient based on low pressure side heat transfer surface B.t.u./ft. hr. F.

h -=High pressure side film coefficient B.t.u./f=t.

hr. F.

h =Low pressure side film coefficient B.t.u./ft.

hr. F.

A=Low pressure side heat transfer surface area ft.

a=High pressure side heat transfer surface area ft.

Since Q=UA, where Q is capacity or heat transfer rate in B.t.u./h. F., then for simplification the following ratio symbols may be employed:

This simplification reduces the equations to the following useful formula:

which equation, provides for a practical expression for the efficiency of the apparatus.

With the foregoing equation in mind, certain objects of the invention are arrived at as follows-the provision of heat exchange apparatus which takes advantage of the allowable pressure drop on the low pressure side independently of the high pressure side, and to avoid losses which do not contribute to the heat transfer. In practice, the low pressure side film coefficient is very small because the available pressure drop is usually low on the low pressure side; thus to maintain the efficiency high, the realization of full advantage to all allowable pressure drop is an important objective of the invention.

Also, from Equation 2, it may be noted. that efficiency is increased directly with the value of h Thus, it is an objective of the invention to take full advantage of the allowable pressure drop on the high pressure side, independently of the low pressure side.

Also, the efficiency may be increased by increasing the value of the ratio (r), i.e., the low pressure heat transfer surface area (A) may be increased relative to the high pressure heat transfer surface area (a). As a practical matter, however, if the ratio (r) is merely increased by increasing the value of A, the bulk, weight, and cost of the exchanger would soon be out of proportion relative to the increase of its capacity (Q). Therefore, the

invention takes advantage of a high value for (r) by first reducing the value of (a), the high pressure transfer surface area commensurate with present day manufacturing capabilities on the one hand and with economy of material on the other hand.

A very significant consideration relative to the heat transfer surface area (a) for the high pressure gaseous stream is stress. This leads to the conclusion that the optimum .shape for the high pressure channel is a circular one and, consequently, preferably tubes are employed as the basic elements for the high pressure gaseous stream in the subject apparatus. Thus, the number of such tubes, their inside diameter, and their length, will determine the numerical value for (a).

Returning to the thermodynamic considerations, since the term (1') must be as large as is feasible, it is desirable to extend the surfaces outside of the tubes which accommodate the low pressure gaseous stream to maximum term (A) in such a way that the low pressure channel will permit the most efiicient use of the available pressure drop.

Prior art heat exchangers, while employing various approaches to extended heat surfaces, nevertheless invariably employ fabricated structural members which receive the full concentrated pressure differential from the high to the low pressure side and the joints of which therefore receive undue pressure forces. Usually such members are box channels of joined planar surfaces or the like which subject brazed junctions to great pressure differentials (the internal forces greatly exceed the external forces) and thus limit the usefulness of the apparatus.

Thus a further object of the invention is to avoid the serious limitations occasioned by working pressures and temperatures which have increased the size and mate-rial requirements of prior art devices and to effect this objective through the shape of constituent parts and the method and means of joining the components to form an exchanger unit.

In contrast to the extra heavy duty materials necessitated in the prior art devices, the present invention enables the use of lighter materials resulting in less cost through the proper selection of the components. Such component design will now be considered. Using the equation for the high pressure side film coefficient h, in terms of the Prandtl and Reynolds numbers, we find the following relation:

h =0.023k/aYP /R (3) wherein the following definitions are given: P,=C /k R =4W/1rdN,u, a=N1rdl N=Number of tubes d=Inside diameter of tubesft.

l=Length of tubesft.

k Thermal conductivity of gases-B.t.u./hr. ftv F. C =Specific heat capacity of gasesB.t.u./lb. F. =Viscosity of gaseslb./hr. ft.

By substituting for the Prandtl and Reynolds numbers, the following equation is obtained:

C=0.0279 (IC'SCP'4/IL'4) (inside tubes) (4) From the foregoing thermodynamic considerations, it is apparent that it becomes important to employ tubes with the smallest possible inside diameter, limited only by manufacturing considerations. Moreover, it is desirable to increase the number of tubes. Further, it is desirable to reduce the term (a) while avoiding unnecessarily high pressure drops. Also, it is preferred to reduce the length of the tubes (1) commensurate with no permissive consideration of possible longitudinal heat leak. Thus, bearing these components design criteria in mind, the invention further has as objects, the following:

The division of total gaseous flow, both on the high and low pressure sides, into an extremely large number of tiny streams, in such a manner that the ratio of the cross-section area divided by the wetted perimeter becomes as small as economically feasible;

Independently to maximize the use of allowable pressure drop on both the high and low pressure sides;

To utilize the counterfiow principle, within practical considerations of both the thermodynamic and manufacturing limitations; and

The use of joining techniques for the components where i which permit assembly line production and best performance under given operating conditions.

Specific components and assembly methods will now be discussed in greater detail. The tubes may be single or multiple tubes, preferably assembled or alined into a plurality of rows, their external cross-sections may be circular, square or rectangular, or otherwise with, preferably, internal circular cross-section of a small diameter. The extended surface takes the form of longitudinal fins, to be packed as densely as possible, in spaced-apart relation relative to the tubes and, preferably, they are longitudinally discontinuous to interrupt any longitudinal heat leak or conductive flow. The fins may be manufactured separately and then joined to the tubes with ease.

Modular units may be built up by including a row of tubes and a plurality of spaced-apart densely packed fins extending longitudinally of the tubes and parallel to the axis of the tubes. Modular structure may alternatively be formed from a row of tubes and a plurality of fins extending from one side of the row or by a row of tubes with a plurality of fins extending from both opposite sides of the row or by a plurality of rows of tubes in parallel spaced-apart relation with fins extending between the rows.

The fins may assume the form of corrugated strips or of corrugated strip-like sect-ions which have been compressed to increase the density or they may be single strips of various configurations.

Preferably during assembly, the fins are brought into intimate contact with the tubes and fixed thereto by a coating of bonding and heat transfer cement or the like, or by a soldering technique to be described. event, the edges of the fins or corrugations may be suitably coated along with the opposite surfaces of the tubes, and the fins then joined to the tubes during assembly.

An alternate preferred method of assembling the fins to the tubes is to form separate layers of the tubes and the fins and to join the layers all at once. This sandwich-type construction permits mass production with attendant cost savings. One manner of effecting the modular assembly is to place thin layers of solder plate or the like between the fins and tubes and even between the fins and the fins where they are to be joined and to mechanically construct the heat exchanger in this modular layer-by-layer fashion until all parts or components are in place. Light pressure externally applied will hold the assembly until permanent joining is effected. Then, a super-heated fluid, such as water, is circulated through the tubes to elevate the temperature of the exchanger,

In any beyond the melting point of the solder, and the heat is removed to permit solidification of the solder, to join all components in a unitary construction at once. Thereafter, of course, if the device is used in refrigeration or cryogenic processes, elevated temperature necessary to unsolder the components are never encountered.

The modular construction so achieved may next be enveloped by a shell or fret which may perform a supporting function and an insulating function to isolate thermally the exchanger from the ambient environment.

Multiple channel heat exchangers may be formed in the above described manner and the tubes or modules are divided into as many groups as there are channels with suitable connections being made to corresponding headers in the manner desired. The particular subdivision of the bundle inside the shell is readily facilitated by the modular construction and can be predetermined for mass assembly. Pretinning facilitates solder for assembly.

The components herein described are susceptible to assembly in heat exchangers in var-ions shapes and sizes and with a versatility heretofore unknown. While such configurations will be described in detail hereafter, it should be mentioned that the straight forward components and assembly methods actually permit the use of aluminum tubes because of the absence of extreme bending requirements such as the usual helical pattern encountered; resulting in weight and cost savings. Also the modular construction permits compact exchangers to be built without sacrifice of the length requirement of the tubes by virtue of configurations to be described, such as a double-back arrangement which affords, for example, three times the effective length of an exchanger at the expense of additional width but may produce an exchanger unit approaching compact square configuration.

With the foregoing in mind the invention will further be described in detail, reference being had to the accompanying drawing wherein:

FIG. 1 is a view in section of a typical tube.

FIG. 2 is a view in section of an alternate tubular configuration suitable-for use in apparatus of the present invention.

FIG. 3 is a view in section of a series of tubes sandwiched between a plurality of radiating fins.

FIG. 4 is a view of an alternate tubular and fin assembly to that shown in FIG. 3.

FIG. 5 is a view, partly in section and partly in side elevation, of a tube with discontinuous longitudinal fins attached thereto.

FIG. 6 is a view in section of a plurality of tubes with a corrugated strip for attachment thereto.

FIG. 7 is a view similar to FIG. 6 showing the corrugation compressed to increase the fin density.

FIG. 8 shows a typical tube with one configuration of a suitable fin attached thereto.

FIG. 9 is a view similar to FIG. 8 showing a different fin configuration.

FIG. 10 is a view similar to FIGS. 8 and 9 and showing a still different fin configuration.

FIG. 11 is a view similar to the next three preceding views with a still different fin configuration being depicted.

FIG. 12 is a view in section of one embodiment of a heat exchanger constructed in accordance with the principles of the present invention and depicting modular units in stacked array.

FIG. 13 is a view similar to that of FIG. 12, but of a further embodiment of the invention.

FIG. 14 is a view in section of a portion of a further embodiment depicting a diflferent type of modular construction.

FIG. 15 is a view similar to FIG. 14, but showing a still different type component arrangement for use in the embodiment of FIG. 14 or as an alternative to the construction shown in FIG. 14.

FIG. 16 is a view in section of a further embodiment of a heat exchanger constructed in accordance with the principles of this invention and showing also how it can be adapted for a low pressure multiple channel use.

FIG. 17 shows a longitudinal sectional view (looking downwardly) of a heat exchanger of the high pressure multiple channel type with facilities for the' collection of condensation or liquid to be tapped oft.

FIG. 18 is a section taken along the plane marked by the arrows 1818 of FIG. 17 to show the internal construction of the exchanger in accordance with FIG. 17.

FIG. 19 is a sectional view seen along the plane 19-19, cutting at the right end a portion of the heat exchanger of FIG. 17 across the header of one channel.

FIG. 20 is a section similar to FIG. 19 but cutting the heat exchanger of FIG. 17 across the header of the other channel.

FIG. 21 is a longitudinal section of a further type heat exchanger employing circular headers and susceptible for multi-channel use.

FIG. 22 is also a longitudinal section of a portion of the heat exchanger structure of FIG. 21 as seen along the plane 22-22.

FIG. 23 is a cross-section of the structure of FIG. 21, as seen along the plane 23--23 thereof, cutting across the header of one channel.

FIG. 24 is a cross-section similar to FIG. 23 but showing the structure of FIG. 21 when out across the header of the other channel, as seen along plane 24-24.

FIG. 25 is a further embodiment of a heat exchanger adapted for use with multiple gaseous streams and capable of gaseous to liquid phase separation.

FIG. 26 is a sectional view, partly in plan, of a compacted heat exchanger of a type capable of presenting extensive tube and fin length without exhibiting extensive external length dimensions, and

FIG. 27 is a sectional view of a portion of the structure of FIG. 26, as seen along the plane 27Z7.

Referring now to the drawings and particularly to the component showings of FIGS. l-ll, the preferred tube and fin configurations and arrangements will be described next.

In FIG. 1 there is shown a cross sectional view of a single tube 3 1 suitable for use as a high pressure conduit in a heat exchanger of the type to be described. It will be appreciated that the tube 31 is of small diameter to withstand the extreme internal pressures desirable to high efficiency operation and still be relatively thin walled, making the apparatus both lighter and more eflicient. The central opening 33 is diminished as far as possible commensurate with present day manufacturing techniques. The inside diameter may be of the order of .010 to /s, such tubes being commercially available in suitable wall thickness.

The material of the tube 31 may be chosen from several materials and consequently may encompass the one best suited to the particular process to be employed. However, it should be pointed out that aluminum tubing may be used because of the component configurations and assembly techniques herein employed. For example, it is unnecessary to wrap the tubes 31 in a spiral or helical configuration. Nor is it necessary to make use of sharp bends. Thus, a considerable savings in weight may be effected in the overall apparatus by employing such light Weight materials.

In FIG. 2 an externally rectangular or square tube 35 is shown in cross section. This type configuration may be used in lieu of the tubes 31 and generally the same dimensions and materials may be employed.

A row of parallelly alined tubes 31 is shown in FIG. 3 to receive spaced-apart fins 37 on opposite sides of the row. Preferably, the fins 37 are joined directly to the tubes 31. One method of effecting this is depicted in FIG. 3 wherein thin layers of solder 39 are disposed on opposite sides of the row of tubes 31 and the fins 37 used as permanent supporting structures.

are stacked against the solder plates 39. Throughout the drawings, the solder plates are shown grossly exaggerated in thickness as in FIG. 3 for purposes of clarity. Also, it should be noted that, alternatively, coatings of heat transfer cement or other materials suitable to metal joining may be employed either along the opposite sides of the tubes 31 or on the ends of the fins 37 to be joined thereto or on both. In any event in the showing of FIG. 3, when the solder is melted the fins are soldered to the tubes directly. Of course, pre-tinning may be additionally or alternatively employed. Moreover, suitable fillers for the arcuate areas between the tubes may be used such that parallel planar surfaces are presented to the layers.

The material of the fins 37 may be varied. It may be selected for suitable joining with the tubes 31 or may be chosen for otherwise emphasized characteristics. Preferably, it is a metal having good heat conductive qualities, such as copper, aluminum or steel.

The fins 37 constitute the extended surface for the component configurations of FIG. 3 and the joining of the'extended surface and tubes may be effected in the following three general ways.

First, frets r shells of an appropriate shape may be The frets are preferably prestressed, either mechanically or by thermal contraction to insure a permanent intimate contact between the tubes and fins.

Secondly, metallurgical techniques may be employed using any suitable method of welding, brazing and/or soldering in accordance with the process requirements, specifications and economic considerations.

Thirdly, chemical techniques such as suitable bonding methods employing an appropriate adhesive or heat trans fer cement may also be used, as may any combination of the aforementioned methods.

In order to facilitate assembly following mass production techniques, the individual fins are not joined to individual tubes, but instead the tubes are alined in alternate layers and the fins are joined thereto all at once. Suitable jigs or fixtures or scored frets are employed to maintain .the spacing of the fins during assembly. While only a relatively few fins 37 are depicted in each tube width, it should be pointed out that in reality, as many as 40 to 80 fins per inch of tube layer width are disposed in intimate contact with the tube to serve as radiators, thereby vastly increasing the extended surface.

FIG. 4 discloses an alternate .arrangement to that described in connection with FIG. 3, the chief difference being the supporting structure 41 which encompasses or surrounds the tubes 31. The material 41 may comprise a solid block which is bored to receive the tubes 31 or it may be fabricable from filler material, heat transfer cement, or the like. Other than serving .to maintain alinement of the tubes 31 in a row, the material 41 also presents opposite parallel planar surfaces to receive the spaced-apart fins 37. While the thin solder plates 39 are shown disposed between the faces of the material 41 and the fins 37, it will be understood that the material 41 alone maybe employed in lieu of the solder plates.

In FIG. 5 there is shown a longitudinal sectional view of a typical tube 31 to reveal a side elevational showing of the preferred fin structure 37. Such a view may be taken along a sectional plane of the structure of FIG. 3, for example, and shows the solder plates 39 on opposite sides of a tube 31, with the interrupted or discontinuous longitudinal sections of the upper and lower fins 37 being apparent. The purpose of the discontinuities is to interrupt longitudinal heat leak such that heat is not conducted along the fins from, for example, the warmer end to the cooler end, of the exchanger, or from the ambient temperatures into the refrigerating region.

FIG. 6 shows a further arrangement of the tube and fin components which arrangement permits the employment of commercially available corrugated structures for the extended surface. The tubes 31 are alined and a suitable filler material 43 is employed on opposite sides of the tubes (only the lower filler being represented) to present a planar, outward surface for the fins. A corrugated piece of material comprising the fin structure is soldered or cemented to the material 43 along its outer planar surface, the solder or cement being depicted by the layer 45, exaggerated showing in thickness. The corrugated structure of the fins 37 is shown also with exaggerated spacings because, in fact it is possible to obtain commercially such material with fine spacing to permit several fins per tube Width. However, other techniques herein described provide better compacting and a greater extended surface, but the structure of FIG. 6 admits of ready assembly and is easily obtained.

For example, one such technique is depicted in FIG. 7 wherein the corrugated material comprising the fins 37 has been compressed in accordion fashion to increase the number of fins iper tube width by several fold. Otherwise, the structure of FIG. 7 is the same as FIG. 6, including the tubes 31, filler 43 and solder plate or a heat transfer bonding material 45.

FIGS. 8-11 show various and suitable individual fin configurations for employment as a component in the exchanger of the present invention. In each drawings, a single fin 37 is shown connected to a single tube 31, but it will be appreciated that in reality the fins are shown grossly enlarged and in fact several such fins are attached to each tube on both sides.

In FIG. 8 the fin 37 carries, on its extreme edges, flanges which provide a greater area for joining the fin to the tube 31 and insure desired spacing of fins.

In FIG. 9 a planar fin 37 is illustrated as being of the simplest and most economical type fin available. FIG. 10 shows one type of reinforcing for the fin 37, and A IG. 11, a further type of ribbing or reinforcing structure formed integrally with the fin 37. In all cases the fins are preferably lightened by the holes 47, which holes help to increase heat transfer and also serve to permit ready access for the low pressure gas to all compartments to avoid any pressure differentials or different pressure drops on the low pressure side throughout the exchanger.

In FIG. 12 there is shown a cross-sectional view taken through a first embodiment of a heat exchanger including the components and illustration of certain principles herein described. A shell or fret 51 encloses four modules 53 of a type made up of a layer of fins 55, a row of tubes 57 and a further layer of fins 55. Between each of the modules there is interposed, for example, attaching means for the modules such as a thin layer of solder or any other heat transfer bonding material 59. Similarly, heat transfer bonding material or solder layers 61 are deployed on either side of the tubes 57 in order that the components of the modules may be built up. Such modules are stacked to form the heat exchanger sectioned in FIG. 12. Around the fret or shell 51 there is disposed a thick layer of insulation 63, in well known fashion, which simply serves to insulate the heat exchanger (from the ambient environment.

In the showing of FIG. 12 the high pressure gas flow, for example, into the sheet via the tubes or conduits 57 and the low pressure gas may flow outwardly of the sheet in the spaces between the fins 55 to provide a useful and efficient counterflow technique.

In FIG. 13 a section through a further embodiment of a heat exchanger manufactured in accordance with the principles herein taught is depicted.

Referring now to FIG. 13, the shell or supporting fret 71 is in the form of a cylinder with insulation 73 being contained around its inner perimeter in the interstices between the assembled modules and the shell 71. The role of insulation 73 is primarily to channel the fiow through the space where the extended heat transfer surface is disposed. It contributes also for sturdiness'bf the construction and for insulation, but real insulation from the surrounding environment must be disposed around the shell 71, as in the case of the FIG. 12 showing.

While the modules, depicted in the brackets '75, substantially correspond to the modules described in connection with FIG. 12, consisting of the spaced fins 55 deployed on either side of a row of tubes 57, it will be appreciated that at the top of the figure an additional layer of fins 55, per se, is shown stacked upon a layer of fins being separated prior to assembly only by the thin solder plate or some other heat transfer bonding material 77. It should be noted that the basic difference between the arrangements of FIG. 12 and that of FIG. 13 is the use of a cylindrical shell which is best suited for withstanding relatively high pressures even on the low pressure side.

In FIGS. 14 and 15 :further sectional views of additional embodiments of heat exchangers are shown. As a matter of fact, both type constructions may be employed in the same heat exchanger and serve as different channels or alternately a heat exchanger may be formed solely from either type construction.

In any event, the modular makeup of the structure of FIG. 14 is slightly different from that previously described because the fins extend between the rows of tubes 57, rather than part way, with a layer of filler 6d therebetween. The basic feature of the arrangements of FIGS. 14 and 15 is to provide the means to insure a good and permanent contact between the tubes and fins through a mechanical compression using the frets 31, while the layers 59 insure a heat transfer balance between the modules and can be used as partitions in case a multichannel heat exchanger is desired on the low pressure side. An alined row of tubes 57 with solder layer or cement coatings or the like is placed on top of the fins 55 and then a further plurality of fins 55, of longer length, is disposed on top of the first row. Thus, the modules are made up of a layer of fins, a row of tubes, a layer of fins, a row of tubes, etc., until the fret 81 is filled. A constraining shell 83 outlines the fret 81 and a thick insulating layer 85 completes the structure.

The alternate structure of FIG. 15 consists of modules, again made up of a layer of fins, a layer of tubes, and a layer of fins, stacked on a layer of fins, a layer of tubes and a layer of fins, etc., in the manner described heretofore.

In FIG. 16 there is depicted a multi-channel heat exchanger in a cross-sectional view, capable of accommodating a plurality of gases and performing a heat exchange function thereamongst. The heat exchanger is comprised of an outside annular shell 91 having heavy insulation 93 generally about its inner perimeter in the interstices between the channels and the shell 91. A right hand channel is constrained by a shell 95 which includes a fret or insert r 97, within which is mounted modules of fins 55 and rows of tubes 57 with filler or solder layers 59 afiixing the fins to the tubes and the fins to the fret. In contiguous relation is a somewhat larger middle channel contained in a shell 101 filled at its extremities by a fret or insert 103 and having deployed therein similar modules of fins and rows of tubes.

Finally, a left hand channel is depicted in a shell 105 including a fret or insert 107 and modules similar to those previously described. In this embodiment three separate heat exchange functions may be carried out simultaneously or multiple gas to liquid phase separation may be carried out in the same refrigeration process.

The same arrangement shown on FIG. 16 can be used when the process requires a relatively high pressure on the low pressure side. In such a case a circular crosssection of the shell 91 is best suited to withstand that relatively high pressure and the shells 95, 101 and 105 are transformed into frets to insure a mechanical joining action between tubes and fins, transmitting their action through the inserts 97, 103, and 197. Then these inserts together with insulation 93 help to properly channel the flow through the space where the fins are disposed. When needed, the shell 91 is enveloped by an outside layer of 1d insulation to protect the apparatus from heat exchange with the surroundings.

The heat exchanger illustrated in FIGS. 17-20 is a high pressure multi-channel variation of a type which may, for example, use high pressure air flow in one direction and its two basic components, oxygen and nitrogen flow, in the opposite direction to etfect contra-flow heat exchange.

In the horizontal sectional showing (looking downward) of FIG. 17, the warm end of the exchanger is depicted to the right. Thus high pressure air may enter this end of the exchanger through a vertical header 121 which is in communication with a plurality of horizontal tube collectors 123. The small arrows 12:5 generally indicate the path of the high pressure air following ingress at the main collector of the header 12. The high pressure air fiows usually downwards.

At the left end of the exchanger, oxygen enters the main collector of the header 127 and follows the arrows 129 to a plurality of tube collectors, such as tube 131. Also, at the cold end, nitrogen enters the exchanger, from a distillation column as the low pressure gas, gaining ingress through the opening 133, as shown by the arrow 135, its flow usually being upwards.

The oxygen may be brought in as a liquid using special pumps and upon evaporation, as it transfers its cold inside the tubes, it may be drawn off to fill oxygen cylinders under a pressure of, for example 2500 p.s.i.

The detailed structure and the paths for the various phases will now be described. A shell or fret 141 generally encloses the heat exchanger and particularly the central bundle or fin area to provide a frame and support. The usual insulation occurring externally of the shell 141 is omitted in the showing of FIGS. 17-20.

The basic modules of this heat exchanger are comprised of rows of tubes with fins spaced on opposite sides of the rows extending to further rows of tubes, as is best illustrated in FiG. 18, wherein the fins 143 are soldered or cemented by layer 145 to the row structure 147, the latter of which may consist of simply alined tubes or tubes set in a filler or solid material as previously described. If the structure were viewed along the plane AA of FIG. 17 it would resemble that of FIG. 12 with the fins following the FIG. 14 teaching.

The fins seen in FIGS. 18, 19, and 20 are not visible in FIG. 17 for they extend downwardly from beneath the tubes exposed in the FIG. 17 showing which may be regarded as a view in plan take just above a row of horizontally alined tubes. These tubes may be designated respectively from top to bottom of FIG. 17 {left to right in the horizontal plan) as an outside high pressure oxygen tube 151, a pair of high pressure air tubes 153, a further oxygen tube and a pair of air tubes 157, with this pattern being repeated transversely of the exchanger. While briefly it depicts a 2:1 ratio of air to oxygen tubes on the high pressure side, it will be appreciated that the ratio may be altered commensurate with the purpose of the device.

The low pressure side of the exchanger utilizes the pathways between the spaced-apart fins 143 (FIGS. 18, 19, and 20) in communication with the ingress 133 (FIGS. 17 and 18) and the right hand egress 159 for the nitrogen leaving the exchanger, as indicated by the arrow 136, the intermediate flow being depicted by the arrows 135' in FIG. 18.

The pathway for the oxygen, be it liquid or gaseous, may best be traced by considering the side elevational or sectional showing of FIG. 18 with the plan or horizontal section of FIG. 17 where it may be seen that the oxygen entering the header 127 emerges therefrom through the openings, such as 16 1 and 163 to follow tubes 152, 154, etc., toward the warm end where it is discharged through the warm end header 171 in communication with a plurality of tube collectors 173. Thus it may be appreciated that approximately /3 of the high pressure tubes extend between headers 12 7 and 17 1 (FIG. 17) to delineate primarily the bundle area therebetween.

a ll

FIG. 20 best illustrates the communication between the oxygen high pressure tubes and the tube collectors 173 as, for example, is shown by the oxygen tube ends 175, 17-7 and 179. Of course, the high pressure air tubes which convey air from the warm end to the cold end of the exchanger (in the opposite direction from the oxygennitrogen flow) have greater overall lengths, as is shown by tubes 153 and 157 which extend from ingress header 121, all the way, to the cold end header 1-81 in communication with the plurality of tube collectors 183.

A feature of the invention can be appreciated from the sectional or side elevational showing of FIG. 18 wherein it can be clearly seen how the air tubes 153, 157, etc., bend only slightly around the oxygen tube collector 161, 163, etc., to maintain the air high pressure paths intact to the egress tube collectors 183. As earlier mentioned, aluminum tubing will readily cope with these slight bending requirements and may therefore be substituted for other materials to reduce the overall weight of the exchanger apparatus.

An alternative heat exchange apparatus to that just described is presented in FIGS. 2l24, wherein the structure may best be illustrated by using the specific example presented in connection with the previously described multi-channel, multi-phase type exchanger. From a consideration of FIGS. 23 and 24, it may be noted that this heat exchanger may assume a circular configuration. FIG. 21 is considered as a plan or horizontal section and FIG. 22 is a side elevational section, preferably taken respectively in planes normal to each other.

Again regarding the right hand end of the structure of FIG. 21, as the warm end of the exchanger, the air inlet may be illustrated as header 201 of annular configuration. Header Ztil has an ingress 2%, at which the high pressure air enters, as is illustrated by the arrow 204 ('FIG. 23). Approximately of the tubes in the central or bundle area of the exchanger of FIG. 21 open into the internal periphery of the annular header 261 to receive the high pressure air at the right hand end of the exchanger. A similar situation prevails at the left hand or cold end of the exchanger where the annular discharge header 205 receives the now pro-cooled air and discharges it through egress 207, as indicated by the arrows 209.

These high pressure air tubes are illustrated in pairs by the following numbers: 211, 212, 213-217, the tubes 217 opening into the discharge annular header 2G5 at 219 and 2 20 in, for example, staggered rows, with the staggering permitting compacting to accommodate the high pressure oxygen tubes which will now be described.

The oxygen, in either phase, is pumped into or allowed toenter the cold end of the exchanger at the annular header 221 through ingress 2212, as is indicated by the arrow 223. The exit for the heated oxygen, which may now be in the gaseous form, is the annular header 225 by Way of the opening 226. As in the case of the previously described exchanger, the ratio of 2:1 is utilized on the high pressure side, for example, such that /3 of the tubes in the bundle section are allotted to the cooling oxygen, with of the tubes containing the high pressure air to be pre-cooled. Thus it may be appreciated that tubes 231, 232, 233-241, are allotted to the oxygen handling.

A typical or exemplary tube for the oxygen is illustrated by the tube 241 which receives liquid oxygen from header 221 via opening 245 and empties the oxygen in the liquid or gaseous phase to opening 247 in exit header 22-5.

The low pressure side of the exchanger of FIGS. 2124 accommodates nitrogen gas flow from the cold to the warm end. Thus it enters ingress opening 251, as is indicated by the arrow 253, and flows through the interstices between the fins 255 (FIGS. 23 and 24). The modules consisting of the fins 255 and tube rows 257 may, of course, assume any of the configurations herein previously described and depicted. Particularly the modular build 12 up of FIG. 13 offers advantages to the circular type exchanger, as was earlier mentioned.

The interstices between the fins 25 5 are in communication with the egress 261 to permit the nitrogen to exit, as is shown by the arrow 265.

In connection with the exchanger apparatus of FIGS. 21-24, it will be appreciated that there is also disclosed an embodiment which absolutely minimizes bends or curves in the tubing and therefore will accommodate aluminum and other light Weight material which is not useful in prior art devices where difiicult configurations are designed into the tubing structure.

A further embodiment of a multi-channel, multi-phase type heat exchanger is illustrated in FIG. 25 wherein use of contra-flow heat exchange between the high and low pressure gases is enabled through bundles of tubes collected for each substance. Otherwise, the exchanger of FIG. 25 may follow the teaching of the two previous embodiments, or alternatively, it may be built up in modular layers, con-forming to the showing of FIG. 25. This view may be regarded as a horizontal plan or section wherein the shell 301 generally bounds the functional components with the exception of external insulation (not shown) and serves as a framework therefor.

Using the same example, helretofore presented the high pressure air may be brought into the apparatus through ingress 3413- and may follow tubes 305 which appear bundled together near the ingress and also at the egress, designated as the opening 3tl7.

The oxygen ingress is provided at the cold end through inlet 309 and the associated high pressure tubes 3 11 extend to the outlet 312 where they are again bunched together in bundle form. The tubes 395 and 311 are preferably disposed in alined rows in a manner heretofore described with the fin areas extending parallel to the plane of the sheet. The ratio of air to oxygen tubes may be set as desired.

The low pressure side of the heat exchanger of FIG. 25 follows the teaching of the previous embodiments, in that ingress for the nitrogen is provided through opening 315 in communication with the spacings between the fins (which appear as the planar surfaces 317 in the showing of FIG. 25) and it exits through opening 319 at the warm end of the exchanger.

It may be noted that the shell 391 may have a rectangular or circular configuration in accordance with either of the prior embodiments set forth herein, and that the embodiment of HG. 25 represents a departure structurewise from that previously disclosed in that substantially right angle bends are shown in the tubing and the various circuits are brought out in the form of bundles at all ingress and egress ends.

As has previously been mentioned, the heat exchanger embodiments described herein are susceptible to ready assembly and such assembly techniques will now further be described. Depending upon the shape and number of tubes, assembling methods to be employed, requisite compactness and process specifications, various type headers will be used. Principally, the joining of tubes and headers is done metallurgically by welding, brazing or soldering.

More particularly, assembly of the exchanger of FIG. 17 is preferably carried out by first joining all the tubes of a single layer belonging to the same channel to the appropriate collector tube. This step is repeated for each layer and separately for each channel. Next, the collecting tubes of the same channel are all joined to the main collecting tube of that channel to comprise the individual headers.

Referring now to the heat exchanger of FIG. 25, the novel method of joining will be described. Each of the headers for the structure is made out of a single piece having a slightly conical shaped inner bore. The ends of all tubes are first cleaned and then pre-coated commensurate with the alloy which will be used for joining. Then all tube ends are assembled into a bundle and introduced into 13 the header where they are held while a melted brazing or soldering alloy is poured to fill all voids and join the tubes and header in one solid piece. Lastly, a conical reduction piece is screwed or welded on the header to permit its manifolding with the pipe system of the installation.

In FIGS. 26 and 27 there is shown a further embodiment of a heat exchanger made in accordance with the principles disclosed herein and which type heat exchanger illustrates a compacting arrangement for shortening a structure without decreasing the effective lengths of the heat exchanger paths. In this embodiment a simple exchange of heat between a low pressure and high pressure gas is contemplated but, of course, the high pressure side admits of division for multi-phase separation if desired. A shell 491 forms a standard or frame for the apparatus and may accommodate insulation internally thereof (not shown) or externally (not shown) or both.

The view of FIG. 26 is preferably considered as a plan or horizontal sectional view wherein the high pressure tubes 403 receive high pressure air through the inlet 405 to convey it to the outlet 407 along a compacted S shaped pathway. The tubes 403 (visible in FIG. 26) represent a horizontal row as is best seen in FIG. 27. The apparatus is constructed with a plurality of such alined rows separated by fins 409 disposed in spacedapart relation. The spacings between the fins 409 accommodate the low pressure side which receives the low pressure gas through opening 411 and discharges the warmed low pressure gas through egress 413.

Other than the compactness afforded by the embodiment of FIGS. 26 and 27, it will be appreciated that a simple straight forward structure is disclosed which admits of ready assembly in modular fashion because the shell 401 is made to receive a layer of fins 4'09 followed by a layer of tubes 403 and a layer of fins 409, with this build-up being repeated until the entire assembly is stacked in the shell. Joining of the fins can be effected as each layer is inserted into the shell 401 by means and methods previously described, or the entire assembly may be put together with solder layers at each junction and the temperature subsequently elevated to permit simultaneous joining of all junctions.

It will be understood that the high pressure gases may be separately fed through alternate rows of tubes in any of the embodiments described, as well as through selected tubes of a given row depending upon the particular application. Of course, additional gaseous streams may be handled in similar fashion.

While the invention has been described in various embodiments, it will be apparent to those skilled in the art that other further embodiments are possible within the principles stated herein, and accordingly it is intended that the invention be limited only by the scope of the appended claims.

What is claimed is:

1. An expensive surface heat exchanger comprising in combination a plurality of small diameter contiguous tubes disposed in spaced-apart alined rows to convey high pressure gaseous flow; means sandwiching the tubes in each row to provide substantially flat surfaces on opposite sides thereof; a plurality of radiating fins affixed in spacedapart relation on each of the surfaces and extending lengthwise of the tubes to guide low pressure gaseous flow and to provide extensive heat exchange surfaces; and means for introducing low pressure gaseous flow between the spaced fins for flow therealong to effect heat transfer with the first-mentioned flow; said tubes being capable of conveying high pressure gaseous fiow without rupture and said fins guiding said low pressure gaseous flow in substantially turbulence-free manner.

2. An extensive surface heat exchanger comprising in combination a plurality of contiguous tubes arranged in spaced-apart alined rows; a plurality of radiating fins in spaced-apart relation along opposite sides of each of the rows and extending along the length of the tubes; means aifixing the fins to the tubes of the rows in the spacedapart relation with a fin density of the order of 40 to fins per inch of the tube Width; to guide low pressure gas stream; said fins having numerable small gaps spaced along the lengths thereof to separate the fins into segments to preclude longitudinal heat leakage; and means for introducing a high pressure gaseous stream to the tubes and the low pressure gaseous stream between the spaced-apart fins for fiow lengthwise of the fins to effect heat transfer between said streams flowing in like or opposite directions only; said fins being relatively smooth for introducing minimal turbulence to said low pressure gaseous stream and said tubes being characterized by minimal diameter to sustain the pressure of said high pressure gaseous stream.

3. An extensive surface heat exchanger comprising in combination a plurality of contiguous small diameter tubes arranged in spaced-apart alined rows and adapted to convey high pressure gaseous streams; .a plurality of radiating fin means disposed in spaced-apart relation along opposite sides of each of the rows with the fin means extending lengthwise of the tubes to guide low pressure gaseous streams; means afiixing the fin means to the tubes of the rows in the spa ced-apart relation to provide a multiple pathways for the low pressure gaseous streams for minimal pressure drop; means enclosing the affixed fin means and tubes from the ambient environment; and means for introducing the high pressure gaseous streams to the tubes and the low pressure gaseous streams to be tween the spaced-apart fin means for flow along the tubes to effect heat transfer between said streams; said tubes being characterized in strength sufficient to contain said high pressure gaseous streams without rupture and said fin means serving to guide said low pressure gaseous streams without introducing substantial turbulence.

4. The heat exchanger of claim 3 wherein the fin means are a plurality of thin substantially planar blades each having numerous narrow control discontinuities in their lengths at spaced intervals therealong to preclude longitudinal heat conductivity.

5. The heat exchanger of claim 3 including a plurality of fins of the order of approximately 40 to 80 fins per inch of tube width afiixed relative to each tube.

6. An extensive surface heat exchanger comprising in combination a plurality of small diameter tubes in each of several spaced-apart alined rows and adapted to convey a high pressure gaseous flow without rupture; means sandwiching the tubes of each row to provide planar surfaces on opposite sides thereof; a plurality of radiating fins extending generally axially of the tubes and disposed in spaced-apart relation on each of the planar surfaces between the rows to provide multiple pathways therebetween for guiding low pressure gaseous flow and provide extensive heat transfer surface, each fin being discontinuous in its length at several locations to provide control gaps which preclude heat transfer therealong; said discontinuities having gap widths relatively small compared to the uninterrupted fin lengths; and means for enclosing the tubes, fins and sandwiching means.

7. An extensive surface heat exchanger for optimizing heat transfer between high pressure gaseous streams and relatively low pressure gaseous streams comprising, in combination a row of tubes extending longitudinally parallel to each other and characterized by small diameter to conduct and contain the high pressure gaseous streams; aflixing means sandwiching the tubes; a plurality of radiating fins in spaced-apart relation for attachment to the tubes by the aflixing means with the fins extending along the lengths of the tubes in alignment therewith to comprise a module; a plurality of such modules in stacked array with the fins of intermediate modules joining respectively the fins of adjacent modules to define a plurality of paths for the high pressure gaseous streams through the tubes and for the low pressure gaseous streams between the fins;

and means enclosing the stacked array to insulate it from the ambient environment; said fins guiding the low pressure gaseous streams and providing extensive heat transfer surface.

8. An extensive surface heat exchanger for optimizing heat transfer between a high pressure gaseous stream and a relatively low pressure gaseous stream comprising, in combination a row of tubes each having a bore less than Mi inch in diameter with the tubes extending longitudinally parallel; parallel planar means sandwiching the tubes; a plurality of radiating fins in spaced-apart relation afiixed to one of the planar mens with the fins oriented lengthwise relative to the tubes to comprise with the sandwiched tubes a module; a plurality of such modules in stacked array with the fins extending between the planar means of adjacent modules to define a plurality of paths for the high pressure gaseous streams through the tubes and for guide the low pressure gaseous stream between the fins;

. and means enclosing the stacked array to insulate it from the ambient environment; said fins guiding the low pressure gaseous streams in substantially turbulence-free manner.

9. An extensive surface heat exchanger comprising in combination a plurality of tubes each defining a single S-shaped configuration and respectively adapted for nesting relation in a common plane; further pluralities of similar tubes respectively arranged in spaced-apart planes with the tubes adapted to convey a gaseous stream; a plurality of radiating fins disposed in spaced-apart relation along opposite sides of each of the planar pluralities of tubes; means affixing the fins to the tubes of the planes in the spaced-apart relation to provide multiple S shaped pathways for a different gaseous stream; means enclosing the affixed fins and tubes from the ambient environment; and means for introducing a high pressure gaseous stream to the tubes and a low pressure gaseous stream to the spaced-apart fins to effect heat transfer between said streams.

10. An extensive surface heat exchanger of a type employing relatively small diameter tubular conduits for containing the high pressure gas flow without rupture and interstices between radiating fins attached to the tubes and etxending lengthwise thereof for guiding the low pressure flow in substantially turbulence free manner comprising in combination a supporting shell; a plurality of said relatively small diameter fin tubular conduits in groups to comprise a plurality of high pressure channels; a plurality of ingress and egress headers for the high pressure channels; said plurality of tubular conduits in communication with the ingress and the egress headers respectively by groups to comprise said channels; and means in communication with the interstices between the fins for providing ingress and egress to the low pressure gas flow.

11. The exchanger of claim 10, wherein each of the pluralities of tubular conduits are bunched together to fit its corresponding header; and, including metal filling in any voids between the bunched tubes and the headers to join the tubes together and to the headers.

12. The heat exchanger of claim 10, wherein the headers of the channels each comprise annular conduits adapted to receive, through openings in their peripheries, the ends of the tubular conduits associated with the channels in communication therewith.

13. A multi-channel extensive surface heat exchanger comprising in combination an outer shell; a plurality of individual shells within said outer shell; a plurality of alternating layers of tubes and attached spaced apart fins disposed within each of said inner shells; said fins extending lengthwise along the lengths of the tubes and between the tubes of adjacent layers; a plurality of conduit means respectively in communication with the interstices between the fins of each of said shells to comprise a plurality of separate channels for low pressure gas flow; and conduit means in communication with selected ones of said tubes for defining high pressure channels.

14. A multi-channel extensive surface heat exchanger comprising in combination an outer shell; a plurality of contiguous individual shells within said outer shell; fret means securing the individual shells within the outer shell; a plurality of alternating layers of tubes and attached spaced-apart fins disposed within each of said inner shells; said fins extending lengthwise along the tubes and otherwise between the tubes of adjacent layers; further fret means locking the tubes and layers in the shells; a plurality of conduit means respectively in communication with the interstices between the fins of each of said shells to comprise a plurality of separate channels for low pressure gas flow; and conduit means in communication with selected ones of said tubes for defining high pressure channels.

15. An extensive surface area heat exchanger comprising in combination a plurality of spaced apart layers of contiguous tubes; a plurality of layers of spaced-apart radiating fins disposed between the tube layers with the fins extending along the tubes and in alignment therewith and afiixed to the tubes; collecting conduits in ingress and egress communication with certain of the tubes of each row; main collecting conduits respectivey in ingress and egress communication with the collecting conduits; further ingress and egrees collecting conduits in communica tion with the remaining tubes of each row; said remaining tubes bending about the collecting conduits for said certain tubes to establish communication with their associated collecting conduits; further main collecting conduits in ingress and egress communication with the collecting conduits for said remaining tubes to comprise a second fluid channel; and means for establishing communication to the spaced-apart fins to establish at least one further fluid channel.

16. The heat exchanger of claim 15 wherein the fins are substantially planar and are disposed in substantially mutually parallel relation to each other and to the axes of the tubes and further comprising means for enclosing the tubes and fins from the ambient environment.

17. An extensive surface area heat exchanger comprising in combination a plurality of layers of tubes; a plurality of layers of spaced-apart radiating fins disposed between the tube layers and afiixed to the tubes; said fins extending lengthwise along the tubes and between the tubes of adjacent layers collecting conduits in ingress and egress communication with a plurality of tubes of each row; main collecting conduits respectively in ingress and egress communication with the collecting conduits; further ingress and egress collecting conduits for other pluralities of tubes of each row; said tubes of the other pluralities bending about the collecting conduits for said plurality of tubes to establish communication with their associated collecting conduits; main collecting conduits in ingress and egress communication with the collecting conduits for the other pluralities of tubes to comprise further channels; partitioning means dividing the tubes and fins into a plurality of compartments; and means for establishing communication to the spaced-apart fins of each compartment to establish low pressure channels.

18. An extensive surface area heat exchanger comprising in combination a plurality of spaced apart layers of tubes wherein the tubes in each layer are contiguously disposed lengthwise; means sandwiching the tubes of each layer to provide planar surfaces on opposite sides thereof; a plurality of layers of spaced apart radiating fins disposed between the tube layers with the fins extending lengthwise along the tubes in alignment therewith and affixed to said planar surface; means enclosing the tubes and fins; means establishing ingress and egress communication with certain of the tubes; further means establishing ingress and egress communication with the remaining tubes; and further means for establishing communication with the interstices of spaced apart fins.

(References on following page) References Cited by the Examiner UNITED STATES PATENTS Goddard 165171 X Ransaur et a1 165157 Scheibel 165-140 X Maetz 165140 X Beck 29157.3

Otten 165166 18 Williams et a1. 165140 Ramen 165157 Boring et a1. 165166 Otten 165140 Whistler 29--157.3

ROBERT A. OLEARY, Primary Examiner.

KENNETH W. SPRAGUE, CHARLES SUKALO,

Examiners.

Butt 165166 10 A. W. DAVIS, AssistantExaminer. 

1. AN EXTENSIVE SURFACE HEAT EXCHANGER COMPRISING IN COMBINATION A PLURALITY OF SMALL DIAMETER CONTIGUOUS TUBES DISPOSED IN SPACED-APART ALINED ROWS TO CONVEY HIGH PRESSURE GASEOUS FLOW; MEANS SANDWICHING THE TUBES IN EACH ROW TO PROVIDE SUBSTANTIALLY FLAT SURFACES ON OPPOSITE SIDES THEREOF; A PLURALITY OF RADIATING FINS AFFIXED IN SPACEDAPART RELATION ON EACH OF THE SURFACES AND EXTENDING LENGTHWISE OF THE TUBES TO GUIDE LOW PRESSURE GASEOUS FLOW AND TO PROVIDE EXTENSIVE HEAT EXCHANGE SURFACES; AND MEANS FOR INTRODUCING LOW PRESSURE GASEOUS FLOW BETWEEN THE SPACED FINS FOR FLOW THEREALONG TO EFFECT HEAT TRANSFER WITH THE FIRST-MENTIONED FLOW; SAID TUBES BEING CAPABLE OF CONVEYING HIGH PRESSURE GASEOUS FLOW WITHOUT RUPTURE AND SAID FINS GUIDING SAID LOW PRESSURE GASEOUS FLOW IN SUBSTANTIALLY TURBULENCE-FREE MANNER. 